Neiman Lab Research


snailsMost research projects in our lab use Potamopyrgus antipodarum, a freshwater snail native to New Zealand. Natural lake populations of this snail vary in the frequency of obligately sexual and obligately asexual individuals, which sets the stage for investigation of why sex persists in some populations but not others. Recent research by our lab has uncovered wide ploidy-level variation within the asexuals, which is of interest both with respect to sex and in terms of understanding the source and maintenance of variation in genome size and structure. While our research is based in evolution, we bring together ideas and tools from ecology, genomics, and behavior to study sex (and ploidy) in P. antipodarum.

ResearcherConsequences of asexuality. One set of projects revolves around testing the hypothesis that asexuality is rare at least in part because sex is required to prevent the accumulation of harmful mutations and facilitate the spread of beneficial mutations. We are using a variety of genetic and genomic approaches to address these questions in P. antipodarum. Related projects assess whether mutation accumulation in asexual P. antipodarum lineages has detectable effects.

ResearcherPotamopyrgus antipodarum genome project ("Potamomics"). We are leading an NSF-funded genome sequencing project for P. antipodarum, in collaboration with John Logsdon (U. Iowa) and Jeffrey Boore (UC-Berkeley). This project promises to provide powerful new resources and important insights into how sexual reproduction and ploidy level variation influence the evolution of genome composition and structure.

collectingDisadvantages of polyploidy. Another major research focus in our lab is centered on the consequences of the higher ploidy of asexual vs. sexual snails. Like most sexual organisms, sexual P. antipodarum have two chromosome sets, while asexual P. antipodarum (like most asexuals) have at least three. Changes in ploidy level can dramatically affect key organismal traits such as cell size, body composition, nutrient requirements, and growth rate. We are currently addressing whether these possible consequences of polyploidy affect asexual P. antipodarum in a manner that could help compensate for the costs of sex and/or influence the distribution of ploidy level variation within and across natural populations.

ResearcherGeneration and maintenance of genome size variation. There is remarkable variation in eukaryotic genome size and structure. Why and how this variation is generated and maintained is not clear, though both adaptive (selection) and non-adaptive processes (e.g., mutation, drift) are likely to play a role. We have found that Potamopyrgus antipodarum harbors extensive genome size variation even within ploidy levels, and are using cytogenetic and genomic approaches to uncover the causes and consequences of this variation.

ResearcherPopulation biology and ecotoxicology. We have used laboratory experiments to discover that growth and reproduction in asexual P. antipodarum is extremely sensitive to population density. We are using population ecology approaches to better understand why and how this happens, especially in light of the fact that P. antipodarum is invading freshwaters worldwide. Because the invasive populations are asexual, our research can help illuminate invasion dynamics as well as sex, and perhaps inspire ideas about how better to control biological invasions. We are also beginning to make forays into ecotoxicology, for which P. antipodarum is growing in prominence as a model system.


Prospective graduate students and postdocs with interests in evolutionary biology and especially the evolution and ecology of sex and ploidy level variation who would like to consider joining our group should contact Maurine Neiman (


Potamopyrgus antipodarum Reproductive Morphology, Anatomy and Mating Behavior (Art by Amanda Nelson and Assata Caldwell; mating behavior videos by Dr. Deanna Soper)